1. Field of the Invention
This invention relates to devices for impeding the spread of fire in a frame structure along a plastic pipe or through an opening in such a structure where a pipe existed previously. If a fire occurs on one side-of the wall or floor defining the opening, experience has shown that plastic pipes, now almost universally used as a building component, either ignite, soften or disintegrate quickly from heat generated by the fire. The present invention provides an apparatus for alternately sealing the opening in the absence of the pipe or simultaneously pinching off the pipe and sealing the opening as the pipe softens, thus preventing flames and heat from the fire from spreading to other parts of the building along the pipe or through the opening.
2. Description of the Prior Art
Following the advent of plastic pipe as a component in residential and commercial buildings, it was soon discovered that the use of plastic pipe unintentionally caused a fire hazard by providing a wick-like conduit for transmitting fire from one part of a building to another and, once the pipe had been removed by the fire or otherwise, an open passageway for fire through a wall or floor. These plastic pipes, commonly made of thermoplastic materials such as polyvinylchloride, polyethylene, are now used, for example, as water and sewer drain lines. Ordinarily, the wall or floor through which a drain line passes must be cut to accomodate the pipe. It is common for the pipe in such a drain line to be 5 inches in diameter or larger. Even when the structure of a wall or floor is basically fireproof, exposure of the plastic pipe to extreme heat situated to one side of the structure causes the pipe there either to ignite or structurally weaken and ultimately to disintegrate, leaving the opening through the fireproof structure formerly occupied by the pipe unobstructed. This opening then allows heat and flames to spread to other parts of the building, negating the intended effect of the fireproof structure.
Various devices have been developed to close off the opening or the section of pipe remaining in the opening after the portion of the pipe subjected to the flame or heat has disintegrated. These devices generally comprise collars or sleeves which fit around the pipe at the opening, or actually extend through a passageway in the wall surrounding the pipe for the length of the passageway.
Wise et al. in U.S. Pat. No. 3,726,050 disclose such a device in which an elongated sleeve extends through a passageway for the pipe. This device includes a weight-loaded or springbiased shutter at each end of the sleeve. As the plastic pipe ignites or is softened by flames or heat, a shutter closes over the respective end of the sleeve. A strong limitation on such a combination is that the device cannot readily be retrofitted onto an existing building. To accomplish a retrofit, the pipe must first be removed so that the opening for it can be enlarged. Unless the opening through which the pipe passes is relatively large, the shutters and their accompanying supports may interfere with the insertion of the device into the opening. On the other hand, the opening must be sized to allow for the snug fitting of the sleeve, since if the sleeve does not fit snugly against the sidewalls of the opening, fire and heat could pass around the outside of the sleeve and thus through the wall. In any event, the sleeve must then be mounted in the opening so that the pipe can pass through it. The device taught by Wise et al. is clearly best suited for installation during new construction and not as a retrofit for existing buildings.
Other prior art devices close off the pipe by providing means for compressing the pipe between two opposed squeezing elements when the pipe sidewalls soften. This type of device is disclosed in U.S. Pat. No. 3,678,634 to Wise et al., U.S. Pat. No. 4,796,401 to Wexler, and U.S. Pat. No. 4,307,546 to Dolder. None of these devices provides for a fire damper that can be readily retrofitted to an existing building structure.
A guillotine-type shutter for closing off an opening occupied by a melting plastic pipe was disclosed by Blumenkranz et al., U.S. Pat. No. 3,462,890. This shutter also included an insulating material for covering the opening left after a softened pipe has been cut by a blade on the shutter. However, Blumenkranz's device has to be installed at the same time the pipe is installed.
Gaillot et al. in U.S. Pat. No. 4,136,707 disclose a combination in which a double gate is employed to close against the melted pipe and a secondary fire stop of a swollen material is employed to close the void left by the burning pipe. This device is particularly suited for use with large plastic pipes and has to be installed with the pipe.